1. Field
The following description relates to an organic light emitting display device.
2. Description of Related Art
Recently, various flat panel display devices, which are lighter in weight and smaller in size than a cathode ray tube display device, have been developed. Here, the flat panel display device may be a liquid crystal display device, a field emission display device, a plasma display panel display device, an organic light emitting display device, etc.
Among the flat panel display devices, the organic light emitting display device displays an image using organic light emitting diodes that generate light by recombination of electrons and holes. Such an organic light emitting display device can be driven with low power consumption, and at rapid response speed.
The organic light emitting display device is provided with pixels disposed in a matrix type pattern. The respective pixels display an image quality that may be predetermined, while controlling the amount of current supplied to the organic light emitting diodes corresponding to data signals. To this end, the respective pixels include a plurality of transistors.
The transistors generally include a semiconductor layer including a source region, a drain region, and a channel region; a gate electrode; a source electrode; and a drain electrode. The semiconductor layer is formed of polycrystalline silicon (Poly-si) or amorphous silicon (a-si). Most of the organic light emitting display devices currently use the polycrystalline silicon (Poly-si) having high electron mobility as the semiconductor layer.
The polycrystalline silicon is generated by forming and crystallizing amorphous silicon on a substrate. Here, various suitable methods may be used for crystallizing the amorphous silicon, such as an Excimer Laser Annealing (ELA) method. The ELA method crystallizes the amorphous silicon as the polycrystalline silicon by emitting laser thereto.
The process of crystallizing the amorphous silicon as the polycrystalline silicon by emitting laser thereto has a great influence on the characteristics of the transistors such as mobility and threshold voltage, etc. Therefore, laser should be emitted uniformly to the transistors.
An ELA crystallization equipment is manufactured to have a predetermined size. Here, when the transistors formed on a large panel are crystallized, laser is emitted thereto by dividing the regions of the panel. Here, a boundary part of the regions is subject to a two-time crystallization process (i.e., subject to a crystallization process and another crystallization process) due to margin errors, etc. of the ELA crystallization equipment. In other words, as shown in FIG. 1, the boundary part of the divided regions of the panel 2 is subject to the two-time crystallization process (i.e., subject to a laser emission and another laser emission). In this case, the characteristics of the transistors positioned on the boundary part 4 of the divided regions of the panel 2 is set to be different from those of the transistors positioned on regions other than the boundary part 4. Therefore, a problem arises in that an image having undesired noise shape is displayed on the boundary part 4 of the divided regions of the panel 2.